JP5459257B2 - Manufacturing method of silicon epitaxial wafer - Google Patents

Description

  The present invention relates to a method for manufacturing a silicon epitaxial wafer, and more specifically to a method for manufacturing an epitaxial wafer using a vapor phase growth apparatus having a lift pin and a lift pin lifting mechanism and having a polysilicon film formed on a susceptor.

A single-wafer type vapor phase growth apparatus is known as a vapor phase growth apparatus for vapor-depositing a single crystal thin film or the like on a semiconductor substrate (hereinafter referred to as a wafer) such as silicon.
This single wafer type vapor phase growth apparatus includes a susceptor in a reaction vessel to which a source gas is supplied, and a mounting surface for mounting a wafer is formed on the susceptor. A lift pin is slidably disposed through a through hole provided in the mounting surface.

  This lift pin is arranged so that its head faces the mounting surface. The lift pins are moved up and down so that their heads are brought into contact with and away from the back surface of the wafer, so that the wafer can be placed on the placement surface and the wafer can be taken out from the placement surface. That is, in a state where the wafer is placed on the head of the lift pin, the wafer is placed on the placement surface by sliding the lift pin and immersing the head on the placement surface. In this way, the wafer is mounted on the mounting surface, the source gas is supplied into the reaction vessel, and the single crystal thin film is vapor-phase grown on the wafer. The wafer after the vapor phase growth is protruded upward by projecting the head of the lift pin from the mounting surface. The wafer thus protruded is transferred out of the reaction vessel by a transfer means such as a handler.

In the manufacture of a silicon epitaxial wafer using a vapor phase growth apparatus, Si is epitaxially grown on the wafer by using a gas such as H ₂ and Si source gases such as SiHCl ₃ , SiH ₂ Cl ₂ , and SiCl ₄ . Since silicon grows in the chamber during this epitaxial growth, it is necessary to periodically remove the silicon grown on the members of this apparatus, and cleaning with HCl gas is performed for this removal.

  In the vapor phase growth apparatus, even a member made of highly corrosion-resistant metal such as SUS is corroded in a high-concentration HCl atmosphere, becomes a gas containing metal (metal chloride, etc.), is taken into the wafer, and the wafer is processed during the epi process. Is contaminated with metal.

  The material of the susceptor is graphite, and there is also carbon contamination due to the susceptor. As described in Patent Document 1, the susceptor surface is coated with a SiC film as a countermeasure against the carbon contamination.

JP 2005-260095 A

  From the viewpoint of reducing the contamination level after HCl cleaning and stabilizing the haze level, a polysilicon film is further grown on the SiC film on the wafer mounting surface of the susceptor, and at the same time, a metal product is coated with a by-product. It is carried out.

  FIG. 3 is a graph showing the relationship between the thickness of the polysilicon film on the wafer mounting surface of the susceptor and the impurity concentration of the silicon epitaxial wafer. As shown in FIG. 3, it can be seen that by forming a thick polysilicon film on the wafer mounting surface of the susceptor, the concentration of impurities such as Ni and Mo taken into the manufactured epitaxial wafer can be suppressed, and the contamination level can be reduced. ing. However, if a thick polysilicon film is grown on the susceptor and the lift pin, the sticking of the susceptor and the lift pin causes the movement to be unstable during the lift pin operation, causing the operation to be unstable, and particles due to peeling of the attached polysilicon. Occurs, the particle level of the manufactured epitaxial wafer is deteriorated, and the operation is stopped due to the operation trouble of the apparatus.

  The present invention has been made in view of the above-mentioned problems, and is capable of stably producing at a low cost by reducing the contamination level while sufficiently suppressing the deterioration of the particle level of the produced epitaxial wafer. It is an object of the present invention to provide a method for producing a silicon epitaxial wafer capable of achieving the above.

  In order to achieve the above object, the present invention comprises a step of growing a polysilicon film by supplying a source gas on a wafer mounting surface of a susceptor having lift pin through holes for allowing the lift pins to pass therethrough, and the wafer A method for producing a silicon epitaxial wafer comprising: placing a wafer on a susceptor having a polysilicon film formed on a placement surface; and vapor-growing an epitaxial layer on the wafer while supplying a raw material gas. A method for manufacturing a silicon epitaxial wafer is provided, wherein the lift pins and the susceptor are relatively moved up and down at least once during the growth of the polysilicon film.

By doing so, even if the thickness of the polysilicon film formed on the susceptor is increased, sticking between the susceptor and the lift pin can be suppressed, so that the operation trouble of the apparatus can be easily performed at low cost. The deterioration of the particle level of the manufactured silicon epitaxial wafer can be suppressed while avoiding the operation stop due to the above.
Furthermore, since the polysilicon film can be made thick regardless of the particle level, a high-quality silicon epitaxial wafer with reduced contamination level, haze level, etc. can be manufactured.

At this time, it is preferable that the polysilicon film is generated from at least one source gas of SiHCl ₃ , SiH ₂ Cl ₂ , and SiCl ₄ .

  In this way, the polysilicon film formed on the susceptor is not removed even during the epitaxial process and does not become an impurity for the wafer to be processed, so that vapor phase growth with higher productivity can be performed.

At this time, it is preferable that the polysilicon film growth step is performed by introducing the source gas into a chamber of a vapor phase growth apparatus heated to 1000 to 1180 ° C.
In this way, the polysilicon film can be formed more efficiently by a simple method.

At this time, when the thickness of the growing polysilicon film is in the range of 8 μm to 20 μm, the lift pins and the susceptor can be moved up and down relatively once or more.
This is preferable because sticking between the susceptor and the lift pin can be suppressed more efficiently.

  As described above, according to the present invention, the silicon epitaxial layer in which the particle level is suppressed can be efficiently vapor-phase grown at low cost, and the thickness of the polysilicon film formed on the susceptor is increased. Therefore, a high-quality silicon epitaxial wafer with reduced contamination level, haze level, etc. can be stably produced with high productivity.

It is a schematic sectional drawing which shows an example of the vapor phase growth apparatus used in the manufacturing method of this invention. It is the figure which showed the incidence rate of the particle in an Example and a comparative example. It is the figure which showed the graph showing the relationship between the polysilicon film thickness and the impurity concentration of a silicon epitaxial wafer.

  Hereinafter, although an example of an embodiment of the present invention will be described in detail with reference to the drawings, the present invention is not limited to this.

  As a vapor phase growth apparatus used in the manufacturing method of the present invention, for example, a single wafer type vapor phase growth apparatus shown in FIG. 1 will be described below, but the present invention is not limited to this, and a vertical type, barrel type, etc. The present invention can be applied even when various vapor phase growth apparatuses are used.

  In the chamber (reaction vessel) 2 of the vapor phase growth apparatus 1 shown in FIG. 1, the susceptor 3 is connected to a wafer rotation mechanism 4, and the wafer rotation mechanism 4 rotates the susceptor 3 during vapor phase growth. The silicon epitaxial layer is vapor-phase grown on the wafer W with a uniform film thickness.

  The susceptor 3 has lift pin through holes 6 for allowing the lift pins 5 to pass therethrough. The lift pins 5 are moved up and down by the wafer lift shaft 7 to move the wafer W placed on the susceptor 3 up and down. be able to.

In the chamber 2, a vapor phase growth gas containing a source gas and a carrier gas (for example, hydrogen) in the chamber 2 is introduced into an upper region of the susceptor 3, and the main surface of the wafer W placed on the susceptor 3. A gas introduction pipe 8 for supplying a source gas and a carrier gas is connected to the top.
A gas discharge pipe 9 for discharging gas from the chamber 2 is connected to the opposite side of the chamber 2 to the side where the gas introduction pipe 8 is connected.

  Hereinafter, although an example of the manufacturing method of the epitaxial wafer of this invention is demonstrated, this invention is not necessarily limited to this.

  Using the vapor phase growth apparatus as shown in FIG. 1, first, before the wafer W is placed on the susceptor 3, the source gas and the carrier gas are introduced from the gas introduction pipe 8, and the wafer placement surface of the susceptor 3. A polysilicon film is grown thereon.

  Here, before forming the polysilicon film, for example, by heating the chamber 2 to 1100 to 1200 ° C. and introducing HCl gas, the polysilicon deposited in the previous manufacture on the inner wall of the chamber 2 is vaporized. It may be removed by etching and cleaned.

  In this cleaning step, the polysilicon deposited on the inner wall of the chamber at the time of vapor phase growth in the previous manufacturing is removed by etching so as not to cause particles or the like of the silicon epitaxial layer. At this time, the metal surface in the chamber 2 is corroded by HCl gas, and in particular, in the first vapor phase growth after cleaning, the corroded metal may be taken into the wafer to cause impurity contamination.

  In order to suppress the contamination as described above, the wafer mounting surface of the susceptor 3 is covered with a polysilicon film generated from the source gas after the cleaning. At the same time, among the members constituting the vapor phase growth apparatus 1, the exposed metal surface of the member whose metal surface is exposed in the chamber 2 is coated with a by-product generated from the source gas. Covered with a membrane. By these, it can suppress that the metal corroded at the time of cleaning is taken in into a wafer at the time of vapor phase growth.

  As a preferable method for forming the polysilicon film and the coating film, first, the inside of the chamber 2 is heated to 1000 to 1180 ° C. At that time, sufficient cooling water is allowed to flow through a metal member such as stainless steel constituting the chamber 2. Next, by introducing the raw material gas from the gas introduction pipe 8, a polysilicon film is simultaneously formed on the susceptor having a high temperature, and a coating film is simultaneously formed on the metal member kept at a relatively low temperature.

Here, it is preferable that the polysilicon film formed on the wafer mounting surface of the susceptor has a thickness of 6 μm or more because the amount of contamination on the wafer can be greatly reduced.
Even if the polysilicon film is formed to have a thickness exceeding 20 μm, there is no problem in the quality of the manufactured epitaxial wafer, but the impurities incorporated in the wafer have already been lowered to the detection limit or lower. In addition to the fact that the improvement of the impurity reduction effect by increasing the thickness of the polysilicon film cannot be expected any more, it is conceivable that the productivity deteriorates and the cost for coating the susceptor, the metal member, etc. increases. Therefore, if the thickness of the polysilicon film is 20 μm or less, it is preferable because it is easy to cover and can maintain high productivity, and it is easy to remove the polysilicon film after vapor phase growth.

At this time, by using at least one of SiHCl ₃ , SiH ₂ Cl ₂ , and SiCl ₄ as a source gas, the polysilicon film formed on the susceptor 3 is not removed even during the epitaxial process, and further on the susceptor 3 thereafter. It is preferable that the wafer W which is placed on the substrate and is subjected to vapor phase growth does not become an impurity and can perform vapor phase growth with higher productivity.

When such source gases such as SiHCl ₃ and SiH ₂ Cl ₂ are thermally decomposed, unstable compounds such as intermediate products such as SiCl ₂ are generated. As a result, Si is deposited on the wafer mounting surface of the susceptor to form a polysilicon film.

  During the growth of the polysilicon film in this way, the lift pins 5 and the susceptor 3 are moved up and down relatively by moving the lift pins 5 up and down by the wafer lift shaft 7 at least once.

By performing such an operation, it is possible to suppress sticking between the susceptor 3 and the lift pins 5 during the growth of the polysilicon film formed on the susceptor 3, so that the particle level can be easily achieved at low cost. An epitaxial layer can be grown on the wafer W while suppressing the above.
The width and speed for moving the lift pin up and down are not particularly limited, and the lift pin may be operated so as to move through the polysilicon film grown on the susceptor and the lift pin through hole formed in the susceptor. .

  The timing for moving the lift pin 5 up and down is preferably when a polysilicon film is grown on the susceptor 3 to some extent. For example, when the thickness of the grown polysilicon film is 8 μm or more and 20 μm or less, at least 1 is used. The lift pin 5 can be moved up and down. When the thickness of the target polysilicon film is 20 μm or more, when the thickness of the polysilicon film increased from the time when the lift pin 5 is moved up and down is 8 μm or more and 20 μm or less again, The lift pin 5 may be moved up and down at least once, and the above operation may be repeated until the polysilicon film reaches the target film thickness.

As described above, after forming the polysilicon film and the coating film, a silicon wafer is placed on the susceptor, and a silicon epitaxial layer is vapor-phase grown on the main surface thereof.
First, the silicon wafer W is put into the chamber 2 in which the charging temperature (for example, 500 to 700 ° C.) is adjusted, and is placed on the wafer placing surface on the upper surface of the susceptor 3 so that the main surface faces upward. Here, hydrogen gas is introduced into the chamber 2 through the gas introduction pipe 8 from the stage before the silicon wafer W is introduced.

Next, the silicon wafer W on the susceptor 3 is heated to a hydrogen heat treatment temperature (for example, 1050 to 1200 ° C.) by a heating device (not shown).
Next, vapor phase etching for removing the natural oxide film formed on the main surface of the silicon wafer W is performed. This vapor phase etching is performed until immediately before the next vapor phase growth.

Next, the temperature of the silicon wafer W is lowered to a desired growth temperature (for example, 1000 to 1180 ° C.), and a source gas (for example, trichlorosilane: SiHCl ₃ ) and a carrier are formed on the main surface of the silicon wafer W through the gas introduction pipe 8. A silicon epitaxial wafer is manufactured by vapor-phase-growing a silicon epitaxial layer on the main surface of the silicon wafer W by supplying gas (for example, hydrogen) substantially horizontally.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.

Example 1
Using the vapor phase growth apparatus shown in FIG. 1, first, the inside of the chamber is heated to 1150 ° C., and HCl gas is introduced, so that the polysilicon deposited on the wafer mounting surface of the susceptor and the inner wall of the chamber is vapor-phase etched. Removed and cleaned.
Thereafter, the inside of the chamber was set to 1100 ° C., SiHCl ₃ was supplied as a source gas from a gas introduction pipe, and hydrogen gas was supplied as a carrier gas, so that a polysilicon film was grown on the wafer mounting surface of the susceptor. Here, as shown in Table 1 below, when the thickness of the growing polysilicon film reaches 8 μm, the lift pin is moved up and down once, and then a 7 μm polysilicon film is grown to obtain the final film. Thus, a polysilicon film having a thickness of 15 μm was formed.

A silicon single crystal wafer having a diameter of 200 mm and a resistivity of 10 Ωcm is placed on the wafer placement surface of the susceptor on which the polysilicon film is formed as described above. SiHCl ₃ was used as a carrier gas to supply hydrogen gas, and epitaxial growth of 10 μm was performed to manufacture a silicon epitaxial wafer.
50 silicon epitaxial wafers manufactured in this way were prepared, and the generation rate of particles generated on these silicon epitaxial wafers was measured. The result at this time is shown in FIG.

(Comparative Example 1)
As shown in Table 1 below, a silicon epitaxial wafer was formed in the same manner as in Example 1 except that the thickness of the polysilicon grown on the susceptor was 8 μm and the lift pins were not moved up and down during the growth of the polysilicon film. Manufactured.
50 silicon epitaxial wafers manufactured in this way were prepared, and the generation rate of particles generated on these silicon epitaxial wafers was measured. The result at this time is shown in FIG.

(Comparative Example 2)
As shown in Table 1 below, a silicon epitaxial wafer was manufactured in the same manner as in Example 1 except that the lift pins were not moved up and down during the growth of the polysilicon film.
50 silicon epitaxial wafers manufactured in this way were prepared, and the generation rate of particles generated on these silicon epitaxial wafers was measured. The result at this time is shown in FIG.

  As described above, it has been found that the greater the thickness of the polysilicon film formed on the susceptor, the lower the contamination level, haze level, etc. of the manufactured epitaxial wafer. However, as can be seen from the results of Comparative Examples 1 and 2, when the polysilicon film is formed thick, the particle level of the manufactured epitaxial wafer deteriorates.

Here, as in the first embodiment, since the lift pins are moved up and down at least once during the growth of the polysilicon film, sticking between the susceptor and the lift pins can be suppressed. It can be seen that even if the thickness is increased, a silicon epitaxial wafer can be produced while suppressing deterioration of the particle level.
In Example 1 above, sufficient results were obtained by moving the wrist pin up and down only once. Since it was not necessary to perform it twice or more, it was performed only once. Of course, it was performed twice or more. May be.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

DESCRIPTION OF SYMBOLS 1 ... Vapor growth apparatus, 2 ... Chamber, 3 ... Susceptor, 4 ... Wafer rotation mechanism,
5 ... Lift pin, 6 ... Lift pin through hole, 7 ... Wafer lift shaft,
8 ... gas introduction pipe, 9 ... gas discharge pipe, W ... wafer.

Claims (4)

A step of growing a polysilicon film by supplying a source gas on a wafer mounting surface of a susceptor having lift pin through holes for allowing the lift pins to pass through;
Mounting a wafer on a susceptor having a polysilicon film formed on the wafer mounting surface, and vapor-phase-growing an epitaxial layer on the wafer while supplying a raw material gas. A method,
A method of manufacturing a silicon epitaxial wafer, wherein the lift pins and the susceptor are relatively moved up and down at least once during the growth of the polysilicon film. The polysilicon _{film, SiHCl 3, SiH 2 Cl 2} , the manufacturing method of a silicon epitaxial wafer according to claim 1, wherein the generating at least one raw material gas of the SiCl _4.   3. The silicon epitaxial wafer according to claim 1, wherein the polysilicon film growth step is performed by introducing the source gas into a chamber of a vapor phase growth apparatus heated to 1000 to 1180 ° C. 4. Manufacturing method.   The lift pin and the susceptor are relatively moved up and down at least once when the thickness of the growing polysilicon film is in a range of 8 μm or more and 20 μm or less. The manufacturing method of the silicon epitaxial wafer of any one of Claims 1.

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